4 HEREDITY AND INHERITANCE 



chrysanthemums, by experimental cleverness and infinite 

 patience, may be surpassed in the future if breeders and cultiva- 

 tors can attain to a better understanding of the more or less 

 obscure laws of inheritance on which all their results depend. 

 Importance in Biological Theory. The study of heredity 

 is also of fundamental importance in the domain of pure science, 

 in the biologist's attempt to interpret the process of evolution 

 by which the complexities of our present-day fauna and flora 

 have gradually arisen from simpler antecedents. For heredity 

 is obviously one of the conditions of evolution, of continuance 

 as well as of progress. There would have been heredity even 

 if there had been a monotonous world of Protists without any 

 evolution at all, but there could not have been any evolution 

 in the animate world without heredity as one of its conditions. 

 The study of heredity is inextricably bound up with the problems 

 of development, reproduction, fertilisation, variation, and so 

 on ; in short, it is one of the central themes of Biology. 



2. What the Terms Mean 



The Terms are tinged with Metaphor. In the popular, if 

 not also in the biological mind, there often lurks the idea of a 

 hypothetical agent possessing the organism and uniting the 

 congeries of its characters. Expressed in diverse ways, there 

 is a prevalent conception of an organismal unity which gives 

 coherence to the sum of qualities (see Sandeman, 1896). Espe- 

 cially in reference to higher animals with a rich mental life, many 

 find it impossible not to think of a " soul " or " self " to which 

 the body belongs. Naturally enough, therefore, the reappear- 

 ance in the offspring of qualities which characterised its parents 

 or its ancestors has been persistently likened to the inheritance 

 of a legacy. But this is to some extent a metaphorical expres- 

 sion, and not without its dangers. 



At first the Organism and the Inheritance are Identical. A 



